1. Field of the Invention
This invention relates to wire connector clips that have two outer legs spaced apart in a plane for insertion of their ends into holes in a support structure to which the legs are to be rigidly attached, part of each leg being curved toward the other leg to join to a reverse-bent portion with two contact regions spaced apart to receive the edge of the conductive structure, such as the edge-connector portion of a printed circuit board, and another part of each leg, located between the curved part and the end of that leg, being formed, as by coining, into a flexure portion of reduced thickness of the wire. Each flexure portion is located between the curved part of the leg and the end, and the direction of the force that produces the thickness reduction is in the plane common to the legs to allow the curved portions, especially the contact regions, of the clip to be moved laterally in the plane relative to the rigidly held ends. In particular, this invention relates to an improvement in clips of the type described in my U.S. Pat. No. 3,340,440 to permit a row of such clips to be soldered to one printed circuit board, but not necessarily in exact alignment with each other, yet with enough flexibility to shift the contact regions so that the straight edge-connector portion of a second printed circuit board can be easily inserted between the contact portions of all of the clips in the row.
2. The Prior Art
Connector clips of the type described in U.S. Pat. No. 3,340,440 are typically mounted individually in printed circuit boards of the type frequently referred to as "mother boards". These are electrically non-conducting boards with conductive interconnections formed thereon to a number of circuits and particularly to connector clips spaced to grasp and make contact with edge-connector pads on other printed circuit boards, known as "daughter boards". In order to accommodate the daughter boards, the individual connector clips must be properly aligned with respect to each other.
While these clips may be made in different configurations, the most common type is M-shaped, with two outer supporting legs and a U-shaped central bight. Physical and electrical contact between each clip and one of the edge connector pads are formed by two small, juxtaposed regions on opposite sides of the U-shaped bight portion. When assembled on a mother board, the outer legs of each clip are rigidly soldered into plated holes in a printed circuit mother board, and the daughter board can later be removably inserted into the central bight portion. The clips may be individually inserted, but there are usually many edge-connector pads on the edge of each daughter board, and the printed circuit boards are normally designed so that there is at least one clip, and sometimes two, to make contact with each edge-connector pad. Since printed circuit boards are usually flat to a high degree of precision, it is essential that all of the contact portions of all of the clips expected to engage the edge-connector pads of a given daughter board will be precisely aligned with each other. The holes into which the outer legs of each clip are inserted are slightly larger in diameter than the legs themselves so that the legs can be inserted easily. However, this makes it possible for the clips that are supposed to be aligned with each other to be slightly out of line when they are soldered into place, thus making an imprecise row into with the daughter board must be fitted. To attempt to fit a daughter board into such improperly located connector clips would require such great pressure to be placed on the daughter board that it would be likely to break either the mother board or the daughter board or, more likely, to be impossible to accomplish. For this reason, it has been the practice heretofore to align a group of connector clips before they are soldered into place and to hold them in such alignment during the soldering operation. They may be aligned by placing a bar or jig of precise thickness in the bight portions of the row of clips and leaving the bar or jig engaged with the clips during the soldering operation.
Such an alignment procedure is unnecessary in the attachment of other components to a printed circuit board and adds an additional step of complexity to the formation of a completed board.
Manufacturers who either make or buy basic printed circuit boards and then insert components, such as integrated circuits, capacitors, resistors, transistors, and other devices into holes formed in specific locations to receive the conductive leads of such components frequently have automatic insertion devices to insert the leads into the proper holes. After all of the components have been put into their proper positions, their conductive leads are simultaneously soldered into position in a wave-soldering device. Since no further mechanical connections are normally expected to be made between such components and any other devices, it is not necessary that the components be located with great precision. However, that is not the case for conductor clips which, as previously described, must be soldered into exact locations to receive the edge-connector pads of another printed circuit board.
The resistors, capacitors, and other devices to be fed into the automatic insertion devices just mentioned are frequently attached to strips of adhesive material would on reels, each of which may contain dozens or hundreds of a specific component. As each printed circuit board passes through the automatic insertion device, the board is brought into a specific position relative to the inserting mechanism, and the leads of the component to be inserted into specific holes in the board in that operation are clipped from the adhesive strip, bent if necessary, and guided into the holes. Then the board is indexed to another position relative to the inserting mechanism and another component is similarly placed in holes formed to receive it.
It would be desirable to use the same sort of mechanism to insert connector clips, but the requirement for high precision in locating the clips has heretofore made it impossible, or at least difficult, to do so.
Various forms of jigs of the type shown in my U.S. Pat. No. 4,061,405 can be used to hold a number of the clips to allow them to be inserted as a group into a printed circuit board and to be held in proper location during the time they are being soldered rigidly into place. However such jigs are not suitable for the type of automatic feeding devices used for insertion of resistors and other such components, and they require either hand assembly or the development of a different type of automatic feeding device.